The urea space 12 minutes after intravenous administration of a defined amo
unt of urea (HVR12) is unsuitable for estimation of body fat content in dai
ry cows. There is no connection between the absolute body fat content and t
he absolute HVR12. Between the relative body fat content and the relative H
VR12 combined a low significant measure of accuracy is established. Bibliog
raphical references about unsatisfactory results by use of this method part
icularly in lactating cows are confirmed.